1.
State what is meant by a gene.
[1 mark]
- a section of DNA that codes for a protein / sequence of amino acids
JD SCIENCE
B5 Genes, inheritance and selection
Indicative marking points. Award marks for equivalent scientific or mathematical wording. Do not issue this sheet with the student worksheet.
2.
State what is meant by an allele.
[1 mark]
- a different version of a gene
3.
State what is meant by a chromosome.
[1 mark]
- a long molecule of DNA that contains many genes
4.
State what is meant by meiosis.
[1 mark]
- cell division that produces four haploid gametes that are genetically different
5.
State what is meant by a mutation.
[1 mark]
- a random change in DNA
6.
State what is meant by natural selection.
[1 mark]
- process where individuals with advantageous alleles are more likely to survive and reproduce
7.
State what is meant by genetic engineering.
[1 mark]
- transferring a gene from one organism to another
8.
State what is meant by a Punnett square.
[1 mark]
- a diagram that shows the possible genotypes of offspring
9.
State what is meant by genotype.
[1 mark]
- the alleles an organism has
10.
State what is meant by sexual reproduction.
[1 mark]
- fusion of male and female gametes
11.
Grace is asked about a gene in a OCR Biology paper.
(a) [2 marks]
- found on a chromosome
(b) [3 marks]
- why a change in a gene can change a protein
12.
Grace is asked about an allele in a OCR Biology paper.
(a) [2 marks]
- can be dominant or recessive
(b) [3 marks]
- why a recessive characteristic only shows if two copies are present
13.
Grace is asked about a chromosome in a OCR Biology paper.
(a) [2 marks]
- humans have 23 pairs
(b) [3 marks]
- why gametes are haploid
14.
Grace is asked about meiosis in a OCR Biology paper.
(a) [2 marks]
- two divisions
(b) [3 marks]
- why meiosis causes variation
15.
Grace is asked about a mutation in a OCR Biology paper.
(a) [2 marks]
- may be harmful, beneficial or have no effect
(b) [3 marks]
- why a mutation in a body cell is not passed to children
16.
Grace is asked about natural selection in a OCR Biology paper.
(a) [2 marks]
- allele becomes more common
(b) [3 marks]
- why antibiotic resistance evolves
17.
In a monohybrid cross Bb × Bb, what fraction of offspring are expected to be recessive?
[3 marks]
- Punnett square
- Final answer: 1/4
18.
80 offspring are produced from Bb × Bb. How many are expected to be heterozygous?
[3 marks]
- 1/2 of 80
- Final answer: 40
19.
A gene has alleles in the ratio 3 : 1 of tall : short. In 200 plants, how many short?
[3 marks]
- Final answer: 50
20.
The chance of a boy is 0.5. What is the chance of two girls in a row?
[3 marks]
- 0.5 × 0.5
- Final answer: 0.25
21.
A DNA sequence is 300 bases. How many amino acids could it code for (ignore start/stop)?
[3 marks]
- triplet code
- Final answer: 100
22.
A population of 400 beetles includes 36 white (recessive). Estimate q² and q if HWE is assumed.
[3 marks]
- 36/400
- Final answer: q²=0.09, q=0.3
23.
Grace carries out modelling meiosis or fertilisation with cards or beads. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: allele combination
- Dependent: offspring genotype counts
(b) [2 marks]
- same number of draws
- so the test is fair / only one variable is changed
(c) [2 marks]
- not replacing / biased shuffling
24.
Grace carries out extracting DNA from fruit. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: fruit type
- Dependent: amount of visible DNA
(b) [2 marks]
- same method
- so the test is fair / only one variable is changed
(c) [2 marks]
- too much blending shears DNA
25.
Grace carries out investigating variation in a class (hand span / height). This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: n/a — observational
- Dependent: measurement
(b) [2 marks]
- same measuring method
- so the test is fair / only one variable is changed
(c) [2 marks]
- inconsistent technique
26.
Grace carries out dissecting a flower to identify male and female parts. This is a typical OCR required-practical style question.
(a) [2 marks]
- Independent: n/a
- Dependent: correct identification
(b) [2 marks]
- same species
- so the test is fair / only one variable is changed
(c) [2 marks]
- damaging the ovary
27.
Compare mitosis with meiosis.
[4 marks]
- mitosis: 2 identical diploid
- meiosis: 4 different haploid
28.
Compare sexual reproduction with asexual reproduction.
[4 marks]
- sexual: variation, two parents
- asexual: faster, clones
29.
Compare dominant allele with recessive allele.
[4 marks]
- dominant expressed in heterozygote
- recessive only in homozygote
30.
Compare natural selection with genetic engineering.
[4 marks]
- natural selection is unplanned over generations
- GE is deliberate transfer of a chosen gene
31.
Apply your knowledge of genetic engineering to this situation: higher yield vs ethical / ecological concerns
[3 marks]
- higher yield vs ethical / ecological concerns
32.
Apply your knowledge of a Punnett square to this situation: fertilisation is random / small sample
[3 marks]
- fertilisation is random / small sample